Interannual Variations in Distribution and Density of Japanese Anchovy ( Engraulis japonicus ) Larvae in the Shelf‐Break Region of East China Sea During Spring (2001–2022)

Abstract

Japanese anchovy ( Engraulis japonicus ) is the most abundant fish in the East China Sea (ECS) and an important fishery resource throughout its life stages. Using samples collected along the ECS shelf‐break in April over a 22‐year period (2001–2022), we examined the horizontal distribution and interannual variability of larval density (mean standard length: 13.8–19.8 mm). High larval densities consistently occurred in the northern ECS off western Kyushu Island, corresponding to the egg distribution observed in March. In the southern ECS (south of 29°30′ N), larvae were primarily distributed along the 100 m isobath. Considering the distribution of eggs and adults in March, these larvae likely originated from local spawning by mature adults present in the region during early spring, potentially including individuals associated with the southward overwintering migration. A substantial proportion of larvae occurring in the southern ECS may recruit to the southern ECS shelf before being transported to the northern ECS. Interannual variations in larval density were not related to habitat conditions (temperature, salinity, or chlorophyll a concentration) but were positively correlated with egg production in March, a proxy for spawning adult biomass. This indicates that variability in larval density is more closely associated with adult biomass than with larval habitat conditions at the spatial and temporal scales considered in this study. Despite differences in the spawning origin, larval density showed a significant positive interannual correlation between the northern and southern ECS, suggesting that adult biomass, spawning timing, and early survival conditions exhibit consistent interannual variability across these sub‐areas.

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